1. Field of the Invention
The present invention relates to a method and apparatus for measuring contact resistances between probes and bonding pads on a semiconductor wafer.
2. Description of the Related Art
Probe testing of integrated circuits requires appropriate management of contact resistances between test probes and bonding pads. The contact resistance between a probe and a bonding pad often suffers from undesirable increase due to various causes, such as wearing and pollution of the probe tip. The increase in the contact resistance may cause inaccurate measurement of integrated circuit characteristics, and therefore monitoring the contact resistance between the probe and the bonding pad is important for appropriate maintenance of the probe tip.
Japanese Laid Open Patent Application No. H02-251162A discloses a technique for contact resistance measurement between probes and bonding pads. This technique involves measuring contact resistances between probes and bonding pads using contact resistance measuring pads which are additionally provided on a semiconductor chip. The above-mentioned application discloses that each bonding pad is connected to one contact resistance measuring pad.
Japanese Laid Open Patent Application No. H08-330368A discloses another technique for measuring contact resistances between probes and bonding pads, in which a pair of monitoring pads are provided for each bonding pad, and used for the contact resistance measurement. The advantage of this technique is that the measured contact resistances between the bonding pads and the probes are almost free from the influence of the contact resistances between the monitoring pads and the probes.
Appropriate management of the contact resistances between probes and contact resistance measuring pads is advantageous in the contact resistance measurement between the probes and the bonding pads. Although being not critical, the increase in the contact resistances between probes and contact resistance measuring pads is undesirable. In order to avoid this, obtaining data indicative of contact resistances between probes and contact resistance measuring pads is advantageous for the appropriate maintenance of the probes, especially, the conditions of the probe tips.
Therefore, there is a need for providing a contact resistance measurement technique which allows obtaining data indicative of contact resistances between probes and contact resistance measuring pads.